The Caterpillars Have Arrived!
The Monarch Life Cycle (technically called metamorphosis) is the series of developmental stages that insects go through to become adults. Butterflies and moths have four stages of life: egg, larva (the caterpillar stage), pupa (the chrysalis phase in a butterfly’s development), and adult. It takes a Monarch butterfly just 28 to 32 days to complete its life cycle. Light, temperature, and humidity all play an important role in determining how long it will take a Monarch to complete its life cycle. Warmer temperatures (so long as it’s not too warm), higher humidity (so long as it’s not too humid), and extra light (so long as it’s not too much light) generally aid in faster development.
Monarch females lay their eggs on milkweed, the only plant monarch caterpillars can eat. The eggs are laid singly and generally on the undersides of leaves. The eggs are very small (about the size of the periods at the end of the sentences on this page) and are white in color. Each egg is attached to the leaf by an adhesive fluid that is applied to the egg as it is being laid.
A day or two before the egg hatches, it turns gray in color. This is because you are actually seeing the tiny dark colored caterpillar inside the egg shell. Four to six days after the eggs are deposited, they should hatch.
A caterpillar spends most of its time eating! Its first meal, immediately after it hatches, is its egg case, which provides it with vital nutrients. Then it starts on milkweed.
Monarch caterpillars feed exclusively on milkweed – making them specialists. They are one of the few species able to tolerate milkweed’s poisonous sap and even to accumulate the cardenolides that make them poisonous in turn.
A caterpillar grows quickly. In 7 to 17 days, its weight increases 2,700 times! To keep up with the growth, its body has to adapt. That means a caterpillar undergoes five successive molts, or instars (also called larval stages).
Each of these molts gives it a slightly larger external skeleton, allowing it to continue growing. The caterpillar’s size may change a lot during each instar, but some of its body parts stay the same. The head and the black filaments get larger only when it molts.
A caterpillar usually leaves the milkweed plant during the fifth instar to go in search of a well-camouflaged spot high off the ground, where it can pupate. Once there, it weaves a tiny silk pad as an anchor. It then inserts the hooks at the tip of its abdomen into the anchor and assumes a J shape. It stays in this position for 12 to 48 hours before extracting itself from its caterpillar skeleton – it is now a pupa.
As the butterfly house progresses, we hope you will join us and enjoy the butterflies.
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